What is the correct way to copy a component?

Question

This question has been on my mind for a long time because the process of copying it does not seem so difficult. Although Unity can easily copy countless components with instantiate code, why do not I see such a feature in a single component?

public class FreeFly : MonoBehaviour
{
    public float wingSpeed = 2f;
    public bool canFly = true;
    
    public void CopyComponent()
    {
        wingSpeed = 10f;
        canFly = false;
        
        var _fly = this;
        var secondFly = gameObject.AddComponent<FreeFly>(); 
        
        secondFly = _fly; // The second component did not register the changes.
    }

    public void Update()
    {
        if (Input.GetKeyDown(KeyCode.Space)) CopyComponent();
    }
}

As you can see, it does not change anything. Interestingly, the Rider IDE also shows it ineffective in code with a yellow underscore.

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What is the best solution?

Considering that variable-to-variable copy is a beginner way, I am looking for a solution that can copy any component using the Generic method. Any help is accepted.

public T CopyComponent<T>(T copyFrom)
{
    // I want this one..
    
    return copyFrom;
}

Answer 1

secondFly = _fly; tells the computer " from now on, if I say secondFly, I mean the Component (Object) that _fly referenced at time of executing this line. " It does not modify the component that was referenced by the variable secondFly , it only changes what secondFly refers to. This is because secondFly is an Object (any type declared as public class ClassName {...} , Component, Rigidbody, etc ), not a primitive type ( int, float, double, byte, etc. ). Variables that are of Object types aren't data themselves, they point to/reference data.

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Beginner Way

You can copy the variables of _fly just like this:

secondFly.wingSpeed = _fly.wingSpeed;
secondFly.canFly = _fly.canFly;

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Advanced Way

Because of the way Unity's Components work, I don't think there's a simple way to duplicate a Component and attach it to a GameObject, but if you don't want to manually copy the variables of the Component, try adding this function to your code and calling it to duplicate your Component (from https://answers.unity.com/questions/458207/copy-a-component-at-runtime.html )

public static T CopyComponent<T>(T original, GameObject destination) where T : Component
{
    var type = original.GetType();
    var copy = destination.AddComponent(type);
    var fields = type.GetFields();
    foreach (var field in fields) field.SetValue(copy, field.GetValue(original));
    return copy as T;
}